1. Field of the Invention
The present invention relates to a safety fuse cartridge, or a cartridge fuse link, which is provided with a porcelain body in which the fuse wire, which is embedded in sand, extends between a lower contact base and an upper contact end or head; the cartridge is provided with a characterizing indication means, which includes a glow lamp which is connected in parallel to the fuse wire via a high-valued resistor.
2. Description of the Prior Art
With a safety fuse cartridge of this general type, which is known from German Offenlegungsschrift No. 31 03 478 belonging to the Assignee of the present application, the small colored plates which have been used for a long time as an indicating pin which is to break when the fuse blows, are replaced by a glow lamp. This glow lamp is connected in series with a high-valued resistor which, in conformity with Ohm's law, is such that, with regard to the current required for the glow lamp, it nullifies the potential difference between the voltage of the line in which the safety fuse cartridge is disposed, and the glow potential of the glow lamp (which is, for example, 60 volts).
With this heretofore known safety fuse cartridge, the optical inspection of the operation thereof is considerably facilitated, since a defective fuse now actively lights up when the fuse is blown (as long as an external short-circuit is still maintained, and/or an external load is connected). Thus it is also possible under conceivable unfavorable conditions to determine reliably whether the fuse is still operable, or whether it has already been blown.
However, a drawback to the heretofore known safety fuse cartridges is, on the one hand, the space arrangement of the high-valued resistor, and, on the other hand, the dissipation of the (joulean) heat generated by this high-valued resistor. Thus, with the heretofore known safety fuse cartridges, a separate hole is provided in the porcelain body for the high-valued resistor; this, however, requires additional expense, namely greater tool costs, greater piece costs for the porcelain body, etc. In addition, the heat generated by the high-valued resistor does not dissipate well, because, as is known, porcelain is a poor heat conductor. Futhermore, this heat dissipation takes place unevenly, because the high-valued resistor, for reasons of installation, is typically disposed purely by chance on a surface line of that inner bore of the porcelain body associated therewith; however, this resistor is otherwise separated from the wall of the inner bore by means of a crescent-shaped air space.
Starting from this, it is an object of the present invention to avoid the drawbacks of the heretofore known safety fuse cartridges, and to provide a safety fuse cartridge which, while being more economical to produce, provides a better heat dissipation of the heat which is produced when the glow lamp burns, i.e. when the fuse is blown.